Question 14 Marks
Find the trigonometric functions of : -210°
Answer

Angle of measure $\left(-210^{\circ}\right)$ : Let $m \angle X O A=-210^{\circ}$ Its terminal arm (ray $O A$ ) intersects the standard unit circle at $P(x, y)$. Draw seg PM perpendicular to the X-axis. $\therefore \triangle O M P$ is a $30^{\circ}-60^{\circ}-90^{\circ}$ triangle. $O P=1$ Ur $=1$ $\begin{aligned} \mathrm{PM} & =\frac{1}{2} O P \\ & =\frac{1}{2}(1) \\ & =\frac{1}{2} \end{aligned}$ $\mathrm{OM}=\frac{\sqrt{3}}{2} \mathrm{OP}$ $=\frac{\sqrt{3}}{2}(1)=\frac{\sqrt{3}}{2}$ Since point $P$ lies in the $2^{\text {nd }}$ quadrant, $x<0, y>0$ $\therefore x=-\mathrm{OM}=-\frac{\sqrt{3}}{2}$ and $y=\mathrm{PM}=\frac{1}{2}$ $\therefore \quad P \equiv\left(-\frac{\sqrt{3}}{2}, \frac{1}{2}\right)$ $\sin \left(-210^{\circ}\right)=y=\frac{1}{2}$ $\cos \left(-210^{\circ}\right)=x=\frac{-\sqrt{3}}{2}$ $\tan \left(-210^{\circ}\right)=\frac{y}{x}=\frac{\left(\frac{1}{2}\right)}{\left(\frac{-\sqrt{3}}{2}\right)}=-\frac{1}{\sqrt{3}}$ $\operatorname{cosec}\left(-210^{\circ}\right)=\frac{1}{y}=\frac{1}{\left(\frac{1}{2}\right)}=2$ $\sec \left(-210^{\circ}\right)=\frac{1}{x}=\frac{1}{\left(\frac{-\sqrt{3}}{2}\right)}=-\frac{2}{\sqrt{3}}$ $\cot \left(-210^{\circ}\right)=\frac{x}{y}=\frac{\left(\frac{-\sqrt{3}}{2}\right)}{\left(\frac{1}{2}\right)}=-\sqrt{3}$
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Angle of measure $\left(-210^{\circ}\right)$ : Let $m \angle X O A=-210^{\circ}$ Its terminal arm (ray $O A$ ) intersects the standard unit circle at $P(x, y)$. Draw seg PM perpendicular to the X-axis. $\therefore \triangle O M P$ is a $30^{\circ}-60^{\circ}-90^{\circ}$ triangle. $O P=1$ Ur $=1$ $\begin{aligned} \mathrm{PM} & =\frac{1}{2} O P \\ & =\frac{1}{2}(1) \\ & =\frac{1}{2} \end{aligned}$ $\mathrm{OM}=\frac{\sqrt{3}}{2} \mathrm{OP}$ $=\frac{\sqrt{3}}{2}(1)=\frac{\sqrt{3}}{2}$ Since point $P$ lies in the $2^{\text {nd }}$ quadrant, $x<0, y>0$ $\therefore x=-\mathrm{OM}=-\frac{\sqrt{3}}{2}$ and $y=\mathrm{PM}=\frac{1}{2}$ $\therefore \quad P \equiv\left(-\frac{\sqrt{3}}{2}, \frac{1}{2}\right)$ $\sin \left(-210^{\circ}\right)=y=\frac{1}{2}$ $\cos \left(-210^{\circ}\right)=x=\frac{-\sqrt{3}}{2}$ $\tan \left(-210^{\circ}\right)=\frac{y}{x}=\frac{\left(\frac{1}{2}\right)}{\left(\frac{-\sqrt{3}}{2}\right)}=-\frac{1}{\sqrt{3}}$ $\operatorname{cosec}\left(-210^{\circ}\right)=\frac{1}{y}=\frac{1}{\left(\frac{1}{2}\right)}=2$ $\sec \left(-210^{\circ}\right)=\frac{1}{x}=\frac{1}{\left(\frac{-\sqrt{3}}{2}\right)}=-\frac{2}{\sqrt{3}}$ $\cot \left(-210^{\circ}\right)=\frac{x}{y}=\frac{\left(\frac{-\sqrt{3}}{2}\right)}{\left(\frac{1}{2}\right)}=-\sqrt{3}$















